Cathode-ray tube



June 12, 1956 R. c. PALMER CATHODERAY TUBE Filed July 2, 1952 Fig.

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P F P F P F INVENTOR.

RICHARD C. PALMER ATTORNEYS United States Patent "Co CATHODE-RAY TUBE Richard C. Palmer, lompton Plains, N. J., assignor to Allen B. Du Mont Laboratories, Inc., Clifton, N. 5., a corporation'of Delaware Application .Iuly 2, 1952, Serial No. 296,857

10 Claims. (Cl. 313-92) The presentinvention relates to cathode-ray tubes and particularly to color-image reproducing cathode-ray tubes.

Heretofore in color television systems, color images of scenes have been reproduced by cathode-ray tubes utilizing screens comprising a plurality of different phosphors or a single color phosphor associated with a plurality of different color filters. Where a single phosphor associated with different color filters have been utilized the filters generally have been attached to the face plate of the tube and have not been entirely satisfactory.

Accordingly, it is an object of the present invention to provide a cathode-ray tube in which the face plate is formed with the different color filters integral therein.

This and other objects may be attained in accordance with the present invention by providing a cathode-ray tube having a face plate of photo-sensitive glass developed to provide the different filter elements integrally therein.

For a better understanding of the invention reference may be had to the drawing in which:

Figure 1 is a longitudinal view' with parts broken away of a cathode-ray tube;

Fig. 2A is an enlarged fragmentary cross-sectional view of the faceplate of the cathode ray tube illustrated in Fig. 1;

Fig. 2B is a plan view of the faceplate shown in Fig. 2A;

Fig. 3A is an enlarged fragmentary cross-sectional View of a modification of the faceplate illustrated in Figs. 2A and 2B;

Fig. 3B is a plan view of the faceplate shown in Fig. 3A;

Figure 4 is an enlarged fragmentary view of another modification of the face plate illustrated in Figure 2; and

Figure 5 is an enlarged fragmentary view of still another modification.

Referring now to the drawing and particularly to Figure 1, there is illustrated a cathode-ray tube comprising an envelope 2 having a neck portion 4 terminating in a base 6. Mounted within the neck portion 4 is an electron gun 8 adapted to direct a beam of electrons on to the face plate 10 of the envelope.

In accordance with this invention, the envelope 2 or the face plate 10 thereof is made of a photo-sensitive glass composition available commercially through the Corning Glass Works of Corning, New York. This glass is one of several types of photo-sensitive glass developed by the above company and has the characteristic when exposed to light and thereafter heat-treated, of developing different colors within the glass itself. It has been found that when glass of this type is exposed to light and thereafter heat-treated a red or blue color may be developed within the glass, the particular color being dependent upon such factors as the amount of light to which the glass is exposed and the time of exposure. Once the glass is exposed to light and thereafter heat-treated the color becomes permanently fixed and endures indefinitely.

2,750,525 Patented June 12, 1956 Referring now to Figs. 2A and 2B of the drawing, there is illustrated inFig. 2A an enlarged cross-sectional fragmentary section of the face plate 10 of the cathoderay tube illustrated in Figure 1, while Fig. 2B illustrates a plan view of the faceplate. The face plate 10 is formed of the photo-sensitive glass composition above described and has been further exposed to light to obtain alternate strips of red and blue colored glass across the face plate of the tube. The desired color of each strip may be attained by providing a mask having elongated portions corresponding to the strips of blue colored glass removed from the mask, and the adjacent areas made opaque to light. The mask may then be placed between a light source which is preferably a source of actinic rays such, for example, as ultra-violet light and the face plate of the tube and the areas of theface plate are then exposed to the actinic rays for a period of time suflicient to develop the latent red color in the glass. Thereafter the mask may be shifted to uncover the unexposed areas, and these areas are then exposed to the actinic rays for a period of time sufficient to develop a latent blue color in the glass. Thereafter the latent colors may be made to develop and fixed in the glass by heat-treatment as herein above described. As shown in Figure 2A, a white phosphor coating is then applied to the inside surface of the face plate. Upon being bombarded by the electron beam, the coating fluoresces and the white light there from passes through the red and blue strips of the face plate where all but the red and blue light is respectively filtered. A cathode-ray tube such as described above is suitable for a two color reproduction of an image.

In Figure 3A there isshown-a modification in which the face plate is exposed to light and heat-treated to provide red and blue'dot' areas, as shown in Fig. 38. Further in this modification the remaining dot areas of the triads are treated todevelop neutral colored dots. In this manner there is provided triads of red, blue and neutral color areas. In a cathode-ray tube having this type of face plate the inside face may be coated with a green phosphor to provide a green color through the triad areas which are neutral. The tube face plate of this modification may be formed in a manner similar to that described in connection with the face plate of Figs. 2A and 2B. In the modification in Figs. 3A and 3B the face plate would be formed by interposing a perforated mask between the source of light and the face plate. The face plate would be exposed through the perforated areas and thereafter the mask would be shifted to permit different light exposures of the several corner areas of the triads and thus develop the red, blue and neutral color areas in the triads.

In Figure 4 the face plate would be formed with color dot triad areas similar to the face plate of Figure 3B but instead of coating the inside surface of the face plate with a green phosphor, a green filter coating is applied and thereafter a white phosphor coating is applied to the inside surface of the filter coating. It should be understood, however, that the green filter may alternatively be attached to the outer surface of the face plate.

Likewise in Figure 5 green filter strips are applied to either the inside or the outside surface of the face plate to cover only the neutral glass areas and a white phosphor coating is thereafter attached as shown. In this figure the green filter has been illustrated as being attached to the inside surface.

A cathode-ray tube such as I have described provides a simple and efficient device for reproducing images in color. Such a tube is particularly desirable in that it does not require forming color phosphor areas on the face plate by processes which are both costly and not suitable for mass production of tubes.

What I claim is:

1. In a cathode-ray tube, a glass envelope having a face plate of light-sensitive glass adapted to provide a plurality of color characteristics therein, said faceplate being photographically fixed to provide a plurality of strips of difierent color filtering characteristics.

2. In a cathode-ray tube, a glass envelope having a face plate of light-sensitive glass adapted to provide a plurality of color characteristics therein, said face plate being photographically fixed to provide triad areas, each triad area having dot areas therein of neutral and different color filtering characteristics.

' 3. In a cathode-ray tube, a glass envelope having a face plate of light-sensitive glass adapted to provide a plurality of color characteristics therein, said face plate being photographically fixed to provide a plurality of adjacent strips of diflEerent color filtering characteristics.

4. In a cathode-ray'tube, a glass envelope having a face plate of light-sensitive glass adapted to provide a plurality of color characteristics therein, said face plate being photographically fixed to provide triad areas, each triad area having adjacent dots of red, blue and neutral color filtering characteristics.

5. In a cathode-ray tube, a glass envelope having a face plate of light-sensitive glass adapted to provide a plurality of color characteristics therein, said face plate being photographically fixed to provide triad areas, each triad area having adjacent dot areas of red, blue and neutral color filtering characteristics and a phosphor coating attached to one side of said face plate, said phosphor coating being adapted to generate predominately green light when exposed to bombardment by anelectron beam.

6. In a cathode-ray tube, a glass envelope having a face plate of light-sensitive glass adapted to provide a plurality of color characteristics therein, said face plate being photographically fixed to provide adjacent strips of respectively red, blue and neutral color filtering characteristics, and a phosphor coating attached to one side of said face plate, said phosphor coating being adapted to generate predominately green light when exposed to bombardment by an electron beam.

7. In a cathode-ray tube, a glass envelope having a face plate of light-sensitive glass adapted to provide a plurality of color characteristics therein, said face plate being photographically fixed to provide adjacent areas of red, blue and neutral color filtering characteristics, a green filter coating attached to said face plate, and a phosphor coating attached to said filter coating, said phosphor coating being adapted to generate white light when ex posed to bombardment by an electron beam.

8. In a cathode-ray tube, a glass envelope having a face plate of light-sensitive glass adapted to provide a plurality of color characteristics therein, said face plate being photographically fixed to provide adjacent areas of red, blue and neutral color filtering characteristics, a green filter coating attached to the face plate to cover said neutral areas only, and a phosphor coating attached to said face plate to cover said filter coating and said red and blue areas, said phosphors being adapted to generate white light when exposed to bombardment by an electron beam.

9. In a cathode-ray tube, a glass envelope having a face plate of light-sensitive glass adapted to provide a plurality of color characteristics therein, said face plate being photographically fixed to provide adjacent strips of red and blue filtering characteristics and a phosphor coating attached to the inside surface of said face plate, said phosphor coating being adapted to generate white light when exposed to bombardment by an electron gun.

10. In a cathode-ray tube, a glass envelope having a face plate of light-sensitive glass adapted to provide a plurality of color characteristics therein, said face plate being photographically fixed to provide adjacent dot areas of red and blue filtering characteristics and a phosphor coating attached to the inside surface of said face plate, said phosphor coating being adapted to generate white light when exposed to bombardment by an electron gun.

, References Cited in the file of this patent UNITED STATES PATENTS 2,518,200 Sziklai et al. Aug. 8, 1950 2,532,511 Okolicsanyi Dec. 5, 1950 2,543,477 Sziklai et al Feb. 27, 1951 2,595,548 Schroeder May 6, 1952 2,684,885 Nakken July 27, 1954 

